1. Field
The present application relates generally to walking assist devices that assist in walking post-injury.
2. Related Art
Crutches are medical devices used when a person has an injured leg or is otherwise unable to use his or her leg. Conventional crutches generally have a single degree of freedom and two endpoints. One endpoint contacts the ground, while the other makes contact with some part of the person's upper body, such as the underarm, and is held by the user's hand. Conventional crutches function by allowing users to put their weight into the crutches, bypassing the injured leg entirely. There are many different kinds of crutches currently on the market; they vary in quality and ergonomic support, and therefore in price. The two most commonly used types are underarm and forearm crutches.
There are many disadvantages to using conventional crutches. The first disadvantage of using conventional crutches is that one must hold onto them, thereby restricting the use of one's hands for other purposes. It is very difficult to walk, stand up, sit down, open and close doors, and climb stairs using crutches. It takes approximately twice the energy to walk with crutches as to walk without them. (See, Fisher, S. V., Patterson, R P (1981); Energy cost of ambulation with crutches; Archives of physical medicine and rehabilitation, 62, 250-56). Conventional crutches depend highly on the user's upper arm strength, which for weak or elderly patients may be a problem. Another problem with conventional crutches is that patients tend to rest their body weight on the axillary pad of the crutch, thereby applying undue pressure. (See, McFall, B., Arya, N., Soong, C., Lee, B. & Hannon, R. (2004); Crutch induced axillary artery injury; The Ulster Medical Journal, 73, 50-52). This pressure damages the arteries in the axillary region. (See, Feldman, D., Vujic, I., McKay, D., Callcott, F. & Uflacker, R. (1995); Crutch-induced axillary artery injury; Journal of Cardiovascular and Interventional Radiology, 18, 296-99). Nerve damage can also result. (See, “Crutch Fitting and Walking”; University of North Carolina at Chapel Hill: Campus Health Services; 2006; <http://campushealth.unc.edu/index.php?option=com_content&task=view&id=102&Item id=65>).
One technological development that has attempted to replace the crutch, as opposed to redesigning it, is called the “iWALKFree”. (See, “iWALKFree High Performance Rehabilitation Device—Hands-free Crutch”; Health Check Systems; 2004; <http://www.healthchecksystems.com/i_walk_free.htm>). This device works by being attached to the thigh while resting the knee, in a bent position, on a flat platform. The “iWALKFree” has the advantage of leaving the hands free, but seems to force the leg to stay in a single, awkwardly bent position. The ground reaction forces are transferred away from the foot of the injured leg and directly into the person's knee joint. With the knee bent, the person's center of mass will be shifted backwards, potentially causing instability. Additionally, the iWALKfree does not contain a knee-like joint, giving it zero degrees of freedom. This “peg-leg” type of design causes the user to experience an abnormal and potentially jarring gait cycle. The design of this device leaves much to be improved upon, while its existence suggests that there exists a need for an alternative to crutches.